Question

How many moles of hydrogen gas are produced when 0.4 moles of sodium react with excess water?

[ 2Na + 2H_2O→ 2NaOH + H_2 ]
a) 0.4 moles
b) 0.8 moles
c) 1.2 moles
d) 0.2 moles

Answer 1

0.4 moles of sodium reacting with excess water produce 0.2 moles of hydrogen gas, as per the 2:1 molar ratio of sodium to hydrogen in the chemical equation.

Step-by-step explanation:

The question asks how many moles of hydrogen gas are produced when 0.4 moles of sodium react with excess water, given the balanced chemical equation 2Na + 2H2O → 2NaOH + H2. To find the answer, we analyze the molar ratio between sodium (Na) and hydrogen gas (H2) in the reaction.

The equation indicates that 2 moles of Na produce 1 mole of H2. Therefore, if 0.4 moles of Na are used, the amount of H2 produced would be 0.4 moles Na × (1 mole H2/2 moles Na) = 0.2 moles of hydrogen gas.